//
//  The MIT License (MIT)
//
//  Copyright (c) 2016 Srdan Rasic (@srdanrasic)
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.
//

import Foundation

/// A proxy protocol for reactive extensions.
///
/// To provide reactive extensions on type `X`, do
///
///     extension ReactiveExtensions where Base == X {
///       var y: SafeSignal<Int> { ... }
///     }
///
/// where `X` conforms to `ReactiveExtensionsProvider`.
public protocol ReactiveExtensions {
    associatedtype Base
    var base: Base { get }
}

public struct Reactive<Base>: ReactiveExtensions {
    public let base: Base
    
    public init(_ base: Base) {
        self.base = base
    }
}

public protocol ReactiveExtensionsProvider: class {}

extension ReactiveExtensionsProvider {
    
    /// Reactive extensions of `self`.
    public var reactive: Reactive<Self> {
        return Reactive(self)
    }
    
    /// Reactive extensions of `Self`.
    public static var reactive: Reactive<Self>.Type {
        return Reactive<Self>.self
    }
}

extension NSObject: ReactiveExtensionsProvider {}

#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)

extension ReactiveExtensions where Base: NSObject {
    
    /// A signal that fires completion event when the object is deallocated.
    public var deallocated: SafeSignal<Void> {
        return base.bag.deallocated
    }
    
    /// A `DisposeBag` that can be used to dispose observations and bindings.
    public var bag: DisposeBag {
        return base.bag
    }

    /// Create a Signal that establishes a key-value observation of the given key path when observed.
    ///
    /// For example:
    ///
    ///     let player = AVPlayer()
    ///     player.reactive.publisher(for: \.status).sink { print("Playback status: \($0)") }
    ///
    public func publisher<Value>(for keyPath: KeyPath<Base, Value>, options: NSKeyValueObservingOptions = [.initial, .new]) -> Signal<Value, Never> {
        return Signal { [weak base] observer in
            guard let base = base else {
                observer.receive(completion: .finished)
                return SimpleDisposable(isDisposed: true)
            }
            let observation = base.observe(keyPath, options: options) { (base, change) in
                observer.receive(base[keyPath: keyPath])
            }
            return BlockDisposable {
                observation.invalidate()
            }
        }
    }
}


#endif
